Bug 26519: Clean up OPAC buttons with incorrect classes

Bug 26519: Clean up OPAC buttons with incorrect classes

This patch makes some corrections to the OPAC templates to add the
correct classes to a few buttons which were missed during the
Bootstrap 4 upgrade, especially in cases where the buttons only appear
when JavaScript is disabled.

To test, apply the patch and rebuild the OPAC CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).

- Locate the bibliographic record for a serial record and view the
  details. The subscription should have patron notification set.
- Under the Subscriptions tab, the "Subscribe to email notifications"
  button should look correct.
- Click to subscribe and confirm that the buttons during and after the
  process look correct.

- Perform a catalog search in the OPAC. On the search results page,
  disable JavaScript. This can be done in the browser's developer tools
  under "Settings."
- At the top of the table of search results there should be a
  correctly-styled "Go" button next to the sorting dropdown menu. It
  should work correctly.

- View the contents of a list with JavaScript disabled.
- The "Resort list" button should be correctly-styled and should work to
  submit the form.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>